Introduction of antiretroviral therapy (ART) has transformed HIV-infection from a fatal to manageable disease but adherence to ART remains critical to optimize outcomes. Existing measures of ART adherence such as self-report, pill counts, electronic pill-bottle caps, and prescription refills, provide only inferred measures of actual drug intake and most offer no real-time notification capability. Directly observed therapy measures actual drug intake but is not practical. These limitations constrain research into medication adherence and more importantly, limit our ability to develop real-time interventions based on feasible, in vivo monitoring of adherence among HIV-infected people to facilitate medication-taking. The Proteus digital health feedback (PDHF) system, a pill ingestible sensor based adherence measuring and monitoring system developed by Proteus Digital Health, addresses these limitations. It involves use of an ingestible sensor, a tiny edible material that i over-encapsulated along with prescribed medication. The sensor is activated by ingestion and is sensed by a patch worn by the patient with an embedded monitor and sensor. The monitor sends a Bluetooth signal to a mobile device, which in turn sends an encrypted message to a central server, thus effecting real-time monitoring that a dose has been taken. We propose to develop a data receiving hub and add to these components an automated text message that is sent to the patient when a dose is missed. The ingestible sensor and patch monitor system is already FDA-approved as safe, but has yet to be tested in HIV- infected patients in clinical setting. The first goals of this study are to confirm the bioavailability of over- encapsulated antiretrovirals (ARVs) and to pilot-test the use of the PDHF system in 15 participants prescribed ARVs to test and identify approaches that optimize the use of this measuring and monitoring system. The next goals are to determine the system's feasibility, acceptability, sustainability, accuracy and efficacy in fostering ART adherence. Feasibility, acceptability and sustainability will be assessed by patients' rating of the system and the rate of dropping off from using the system. Accuracy will be evaluated by the associations between adherence to ART measured by the PDHF system and other adherence measures such as plasma drug level concentrations of ARVs and self-report. Efficacy will be assessed by comparing adherence of participants assigned to the PDHF system and participants assigned to usual care (UC) over time, with exploratory outcomes of viral load and CD4. We will recruit 120 of HIV-infected patients 18 years or older with sub-optimal adherence. Participants will be randomized to receive the PDHF system or UC for 16 weeks with monthly assessments. The durability of effects of the PDHF system after stopping the use of the system will be determined during a 12-week follow-up stage. In summary, we will evaluate the feasibility, acceptability and sustainability of using the PDHF system; assess the accuracy of the PDHF system in measuring adherence to ART; and evaluate the efficacy of the PDHF system for monitoring and leveraging adherence to ART. 1